1. Field of the Invention
This invention relates to an improved intermittent patient suction system and to an improved control means therefor.
2. Prior Art Statement
It is well known to provide an intermittent suction system for alternately applying a vacuum and atmospheric pressure to a patient for removing fluids from the patient and comprising a vacuum source and first and second container means adapted to be interconnected to the source and to the atmospheric pressure by control means that is adapted to apply the vacuum to the patient in response to a vacuum condition in the first container means and to apply the atmospheric pressure to the patient in response to a vacuum condition in the second container means.
For example, see the following item:
(1) U.S. Pat. No. 3,659,605--Sielaff.
It appears that the intermittent patient suction system of Item (1) above includes four like relay units in the control means thereof with each control unit including a spring means which must be overcome in order to provide the switching function for applying the vacuum to the patient as well as for applying the atmospheric pressure to the patient.
For example, see the following item:
(2) U.S. Pat. No. 3,754,572--Scott.
It appears that each of the relay logic units of Item (1) above are of the type in Item (2) above where the switching diaphragm is spring biased to one position thereof and the force of the spring must be overcome by a resulting pressure differential created by two different vacuum sources being imposed on different sized diaphragm portions thereof.
It was suggested by another that perhaps the switching relay of Item (1) could be modified so that the control means would always interconnect the vacuum to the patient when the vacuum condition of the first container means is a certain percentage of the vacuum condition of the sorce regardless of the vacuum value of the source.
However, such suggestion did not provide any information as to how the physical structure of such relay of Item (1) above and as of the construction of Item (2) above could be modified to produce such desired results.